Support for formatting (and converting) labels of attributes

[szekerest]

Mapserver supports displaying labels based on attributes in different ways, that
is specifying labeitem or setting up the text attribute of the class. The latter
allow of labeling based on multiple attributes.

In many cases it would be useful to convert the type of the attribute (eg. from
float to integer) value and (or) to apply some formatting on numeric fields(eg.
number of digits or floating point representation) before drawing it.

In the current implementation mapserver reads attribute values as strings so
formatting takes place at the driver level. In order not to rewrite large amount
of code atof or atoi could be used before applying the formatting after
evaluating the users format specification given along with the field names.


Tamas